UV Liquid Steriliser

ABSTRACT

A fluid treatment apparatus for sterilizing drinks comprises an elongated tubular duct ( 110 ) and an elongated UV light source ( 111 ) extending longitudinally along the duct ( 110 ). The fluid flows longitudinally along the duct ( 110 ) in a thin annular low passage ( 114 ) which extends around the UV light source ( 111 ). A mixing device ( 112 ), disposed between adjacent longitudinal portions of the duct ( 110 ), diverts the fluid from a first portion of the passage ( 114 ) through fluid mixing means ( 113, 116 ) in the device ( 112 ) and returns the mixed fluid to a second portion of the passage ( 114 ). Micro-organisms in the fluid flow are killed as they come close to the light source ( 111 ). The mixing device ( 112 ) mixes the flow and returns it to the flow passage ( 114 ). A plurality of mixing devices along the duct ( 110 ) increases the likelihood that microorganisms receive a sufficient lethal dose of UV radiation.

This invention relates generally to the disinfection of fluids, and moreparticularly, but not solely to the disinfection of drinks and liquidouscomestible.

At present the pasteurization technology for the drinks industryutilises thermal pasteurization, whereby a drink is elevated to atemperature which kills the micro-biological contamination in the drinkand renders it fit for human consumption.

The following problems exist with thermal pasteurization technology:

1) Thermal pasteurization processes destroy some of the naturalingredients of the drink sometimes requiring the drink to bereformulated post disinfection to provide an acceptable tasting drinkfor the public. Often this requires chemical additives.

2) The taste of the drink is generally degraded from its originalflavour.

3) A substantial amount of energy is required to thermally pasteurize aliquid.

4) The thermal energy required to pasteurize the drink is often removedby refrigeration before the bottling operation: this is a very energyinefficient and costly process.

5) Thermal pasteurizers require regular cleaning because someconstituents of the drink bake onto the inside of the heat exchanger inthe thermal pasteurizer and must be removed.

6) Drinks manufacturers often develop drinks which have market potentialonly to find that the drink is destroyed in the thermal pasteurizationprocess.

7) The thermal pasteurization process does not kill all of the microorganisms encountered in the drink products e.g. the spores ofalicyclobacillus, a spoilage organism effecting apple and orange juice,are unaffected by the thermal pasteurization process and can result indanger to public health and major product recalls for the drinksmanufacturers.

It is well known that UV wavelengths in the range 220 nm-280 nm(germicidal wavelengths) kill all micro organisms. Such wavelengths willonly disinfect if sufficient radiation penetrates the liquid. Theliquids in the drinks industry are generally high absorbers of UVgermicidal radiation (220 nm to 280 nm) and therefore UV lightpenetration into these liquids at such wavelengths is poor. For examplethe penetration of 254 nm though milk is very poor, with 90% of theincident radiation being absorbed in the first 0.01 mm penetration.

WO2006106363 and EP2055317 disclose apparatus which attempt to solvethis problem by creating a thin film of the liquid to be treated andexposing the film to UV light in the germicidal wavelength. When semiopaque liquids are formed into thin films the UV light penetration atthe germicidal wavelengths increases, this is a partial solution butdense liquids such as milk or sauces cannot be disinfected by this UVlight, thin film irradiation technique alone. For high absorbing liquidsthe thin film must be thoroughly mixed as it is being disinfected, thisdiminishes the importance of UV light penetration and converts theprocess into substantially a UV surface disinfection technique.

Apparatus of the kind disclosed in WO2006106363 and EP2055317 have poorreliability due to complex mechanisms and many of moving parts.Furthermore the apparatus could not withstand the high pressures (up to10 bar) used in the industry standard cleaning-in-place CIP process.

Patent no. US 2009081340, discloses an apparatus which comprises astainless steel rotating inner cylinder and a stationary transparentouter cylinder. The liquid is introduced into the gap between the twocylinders and is irradiated by UV lamps through the stationarytransparent outside cylinder. The intention of the rotating innercylinder is to impart mixing to the liquid. The system is finelybalanced with the throughput flow and the speed of rotation of thecylinder dictating the volume of liquid that can be disinfected, whichfor adequate mixing results in small volume throughput and hence is notcommercial.

The rotating element requires that the thickness of the liquid film mustbe kept to a practical size for mechanical reliability requirementswhich conflicts with the principle of good disinfection of high absorberliquids i.e. thin liquid films for best light penetration, this systemcannot be cleaned in place (CIP) as it cannot survive the high pressures(up to 10 bar) used in the industry standard CIP process.

The foregoing are problems which are common to previous attempts tosolve the UV disinfection of semi opaque and opaque liquids.

The object of the present invention is to provide a low temperaturedisinfection system, with no moving parts and which can withstand theindustry cleaning pressures. The present invention must be able toproduce a consistent thin film of liquid which is continually andthoroughly mixed as the liquid flows through the system in high volumes.

I have now devised a disinfection apparatus for high UV absorber fluidswhich does not rely on thermal pasteurization and meets theaforementioned criteria.

In accordance with the invention there is provided a fluid treatmentapparatus, comprising an elongate tubular duct having a fluid inlet andoutlet at opposite ends thereof an elongate source of UV radiationextending longitudinally of said elongate tubular duct, and a mixingdevice disposed between adjacent longitudinal portions of the duct fordiverting all of the fluid flowing along a first said portion of theduct through fluid mixing means in the device and for returning themixed fluid to a second said portion of the duct.

The mixing of all the fluid ensures that all parts of the fluid comewithin sufficient proximity of the UV source.

Preferably said mixing means defines a tortuous flow path through whichthe fluid flows, the flow along the passage serving to provide a highdegree of mixing.

Preferably the flow path comprises one of more turns of 90° andpreferably the flow passage turns the fluid though at least 180° betweenadjacent longitudinal portions of the duct. Good mixing of a liquid canbe achieved by continually changing its direction through 90° bends orpreferably through 180° bends. The continual sudden velocity changesimparted to the liquid by this technique ensures all constituents of theliquid are mixed.

Preferably at least a portion of the flow path is arranged to beirradiated by UV radiation emitted by said source.

Preferably the duct defines a flow passage for the fluid in which all ofthe fluid is no more than 10 mm and preferably no more than 5 mm awayfrom the surface of the UV source, the source forming at least a portionof the longitudinal wall of the flow passage. In this way the fluidflows as a thin film over the UV source. The surface constituents of thethin film are continually being changed due to the mixing effect.

Preferably the UV source extends along the central axis of the duct andis surrounded by the flow passage.

Preferably the UV source comprises an elongate lamp disposed inside atube which is preferably formed of quartz or another material which is agood transmitter of UV radiation.

Preferably the tube is coated or covered with a material arranged tomaintain the integrity of the tube should it break, thereby preventingcontamination of the fluid with potential harmful pieces of the tubematerial. Preferably the coating or covering material comprisesfluorinated ethylene propylene.

Preferably a plurality of said devices are provided along the length ofthe duct so that the fluid is mixed more than once.

Preferably the inlet and outlet communicate with respective manifolds atopposite ends of the duct.

Preferably the UV source extends into one or both manifolds.

Also, in accordance with the invention, there is provided a fluiddisinfection system comprising a plurality of the above-mentionedapparatus connected in series to increase the disinfection effect or inparallel to increase the flow rate of the disinfected fluid or both.

A summarisation of the invention and the benefits thereof is as follows:

-   -   Disinfection system with no moving parts—all parts are        stationary therefore the reliability of the system is high.    -   Room temperature (change to cold) disinfection system—the        process is substantially a cold process.    -   Can withstand the industry cleaning pressures—all parts are able        to withstand pressures of 10 bar and beyond.    -   Produces a consistent thin film of liquid—the gap between the        quartz tube and the inner surface of the duct provides a        consistent liquid film thickness.    -   Continually and thoroughly mixes the fluid—The mixing devices        are placed at intervals along the length of the apparatus        forcing the fluid to change direction and hence the fluid        velocity ensuring constant and thorough mixing of the fluid as        it flows through the system.

Embodiments of this invention will now be described by way of examplesonly and with reference to the accompanying drawings, in which;

FIG. 1 shows a plan view with part section of a first embodiment offluid disinfection apparatus in accordance with the invention;

FIG. 2 shows a plan view with part section of a second embodiment offluid disinfection apparatus in accordance with the invention;

FIG. 3 shows a plan view with part section of a third embodiment offluid disinfection apparatus in accordance with the invention;

FIG. 4 shows an exploded view of one kind of mixing device for a fluiddisinfection apparatus in accordance with the invention;

FIG. 5 shows an exploded view of another kind of mixing device for afluid disinfection apparatus in accordance with the invention;

FIG. 6 shows a sectional view of a fourth embodiment of fluiddisinfection apparatus in accordance with the invention;

FIG. 7 shows a plan view of the apparatus of FIG. 6;

FIG. 8 shows an exploded view of a portion of fifth embodiment of fluiddisinfection apparatus in accordance with the invention; and

FIG. 9 shows an exploded view of a portion of sixth embodiment of fluiddisinfection apparatus in accordance with the invention.

Referring to FIG. 1 of the drawings in the first embodiment of the fluiddisinfection apparatus a reaction chamber 1 is connected between endplates 2 & 3. Preferably the reaction chamber is welded to the endplates such that the welds are polished to provide a hygienic food gradeseal.

Positioned adjacent to the reaction chamber is an inlet manifold 4 andan outlet manifold 5 which are attached to the end plates 2 & 3 byfastenings 6. The inlet manifold 4 and outlet manifold 5 are madewatertight by seals 7 & 8 which are clamped between the inlet and outletmanifolds 4 & 5 and the end plates 2 & 3.

A tubular sleeve 11 is positioned longitudinally centrally andconcentrically inside the reaction chamber 1 such that it protrudesthrough the end plates 2 & 3 and through the holes 9 & 10 in the inletand exit manifolds 4 & 5.

Preferably the tubular sleeve is a good transmitter of the germicidalwavelengths (220 nm-280 nm).

Preferably the tubular sleeve is made of quartz.

Preferably the quartz sleeve is coated with a material whichsubstantially transmits the germicidal wavelengths.

Preferably the coating material is substantially resilient in nature andis able to contain all quartz debris in the event of the quartz tuberupturing.

Preferably the material is Teflon FEP.

Means are provided to form a small concentric gap 12 between the tubularsleeve 11 and the inside wall of the reaction chamber 1. By selectingthe dimensions of the outer diameter of the tubular sleeve 11 to beslightly smaller than the inner diameter of the reaction chamber 1, thegap 12 produced is the dimensional difference between the two.

Means are provided to make a water tight seal between the tubular sleeve11 and the inlet and outlet manifolds 4 & 5 in the form of a seal 13 &14 positioned on the circumference at each end of the tubular sleeve 11adjacent to the holes 9 & 10 in the inlet and outlet manifolds 4 & 5.The seal is compressed by clamping plates 15 & 16 forming a watertightseal between the inlet and outlet manifolds 4 & 5 and the tubular sleeve11.

The reaction chamber 1, tubular sleeve 11 and the inlet and outletmanifolds 4 & 5 form a watertight assembly such that liquid can flow inthrough the inlet manifold 4, through the gap 12 and out through theoutlet manifold 5.

Preferably the seals 13 & 14 are made of UV resistant material.

Preferably the material is silicone rubber, Viton, PTFE or Teflon FEP.

Preferably the seals 13 & 14 are designed to be flexible such that anydifferential expansion between the body of the reaction chamber 1 andthe tubular sleeve 11 is accommodated whilst the seals 13 & 14 stillremain sealed.

Means are provided to radiate UV germicidal wavelengths (220 nm-280 nm)into the gap 12 in the form of a UV lamp 17 positioned inside thetubular sleeve 11 which when energised radiate germicidal wavelengthsinto the gap through the wall of the tubular sleeve 11.

Preferably the lamp 17 is positioned longitudinally centrally andconcentrically inside the tubular sleeve 11 to provide consistent andeven radiation into the gap 12.

Means are provided to mix the liquid as it passes through thedisinfector in the form of mixing devices 18 positioned along the bodyof the reaction chamber 1 whereby the flow in the gap 12 is divertedinto and through the mixing device 18. The mixing device 18 forces theliquid to traverse a flow path which causes it to change direction andhence velocity to create a thorough mixing of the fluid as it passesthrough the device.

Preferably the mixing device 18 has no moving parts.

Preferably the mixing device 18 forces the liquid into at least one 180°bend

Preferably the mixing device 18 is made of material which issubstantially resistant to germicidal radiation.

Preferably the outside body of the mixing device 18 is made of a foodgrade standard material.

Preferably the outside body of the mixing device 18 is made of 316 gradestainless steel.

Preferably the internal materials of the mixing device 18 are made ofPTFE or Teflon FEP or another suitable material.

The general fluid flow is shown by the arrows A & B and the interveningarrows.

Referring to FIG. 5 of the drawings shows a mixing device for theapparatus comprising circular flanges 2 & 3 attached to the body of thereaction chamber 1.

Flange 2 has shallow grooves cut into its face which act as channels forthe liquid. The top groove 4 rises vertically from the centre of theflange 2 then moves in an arc in a clockwise direction for a distancearound the top face of the flange 2. The bottom groove 5 fallsvertically from the centre of the flange 2 then moves in an arc in aclockwise direction for a distance around the bottom face of the flange2.

Flange 3 has a mirror pattern of grooves (not shown) cut into its facesuch that the grooves match each other when the flanges are fastenedtogether.

Positioned through the centre of the reaction chamber 1 is the tubularsleeve 11 as described previously, which with the reaction chamber 1provides the gap 12.

Interposed between the two flanges is a disc 6 which has a series ofholes 7 & 8 positioned so that they line up with the ends of theclockwise arcs in the two flanges 2 & 3 when the mixing device isassembled. The centre hole 10 in the disc 6 is a tight fit on thetubular sleeve 11. When the mixing device is assembled the disc 6substantially acts as a deflector for the liquid in the gap 12 divertingit out of the gap 12 and into the grooves 4 & 5 and holes 7 & 8.

Assuming that the liquid is moving from right to left in gap 12 of thereaction chamber 1, the disc will force the liquid into the grooves 4,in flange 2, through the holes 7 & 8 in the disc 6 and back along themirrored grooves in flange 3 and into the gap 12 in the reaction chamber1.

A flow schematic sketch 9 shows the fluid path through the device

The liquid will have had three complete reversals of flow through themixing device. A—90° change in direction from the gap 12 to the verticalgroove on flange 2, B—90+ change in direction from vertical groove onflange 2 to the clockwise arc on flange 2, C—90° change in directionfrom the clockwise arc on flange 2 to the holes 7 in the disc 6, D—90°change in direction from the holes 7 in the disc 6 into the mirrored arcin flange 3, E—90° change in direction from the mirrored arc in flange 3to the mirrored vertical groove in flange 3, F—90° change in directionfrom the mirrored vertical groove in flange 3 to the gap 12.

Preferably the disc is made of a UV resistant material.

Preferably the disc is made from PTFE or Teflon FEP

The mixing device has an additional feature in that after CIP (clean inplace—the drinks industry standard cleaning process) the unit selfsterilizes if at the end of the cleaning cycle it is filled with waterand the lamp is switched on for a period of time, there is enoughradiation to reflect through the mixing device to disinfect it.

FIG. 5 only shows one disc 6 but a plurality of discs can be positionedin series to increase the level of mixing of the fluid.

Those skilled in the art will appreciate that the mixing effect can beaccomplished with many different labyrinths like patterns in the mixingdevice of which the general theory of the invention covers.

Referring to FIG. 2 of the drawings there is shown a second embodimentof a mixing device apparatus comprising a plurality of fluiddisinfection apparatuses as described previously but whose inlet andoutlet manifolds 5 & 6 act as conduits to allow the fluid disinfectionapparatus to be connected in series.

Fluid flows from A into the gap 12 and then into the first mixing device18 in the first fluid disinfection apparatus and continues along the gap12 and through each mixing device 18 in turn until it flows into theexit manifold 5. The fluid then flows through the exit manifold 5 andinto the gap 12 of the second fluid disinfection apparatus and the thenflows in turn through each mixing device 18 in the second fluiddisinfection apparatus until it reaches the second fluid disinfectionapparatus's exit manifold 19.

The process repeats for as many fluid disinfection apparatuses areconnected together.

As the fluid passes through the gap 12 it is irradiated by thegermicidal wavelengths radiating from the UV lamp 17 and through thewall of the tubular sleeve 11 to provide a very effective disinfectionof the fluid film.

Several of these fluid disinfection apparatus arrays can be connectedtogether in parallel to increase the flow handling capability of thesystem.

Referring to FIG. 3 of the drawings showing the third embodiment of thefluid disinfection apparatus, a plurality of fluid disinfectionapparatuses are constructed such that the fluid disinfection apparatusesare connected in series. Each fluid disinfection apparatus feeds it flowinto another fluid disinfection apparatus.

Each fluid disinfection apparatus consists of a reaction chamber 1rigidly connected between end plates 2 & 3.

Preferably the reaction chamber is welded to the end plates such thatthe welds are polished to provide a hygienic food grade seal.

Positioned adjacent to the reaction chamber is an inlet manifold 4 andan outlet manifold 5 which are attached to the end plates by fastenings6. The inlet manifold 4 and outlet manifold 5 are made watertight byseals 7 & 8 which are clamped between the inlet and outlet manifolds 4 &5 and the end plates 2 & 3.

A tubular sleeve 11 is positioned longitudinally centrally andconcentrically inside the reaction chamber such that it protrudesthrough the end plates 2 & 3 and through a hole 9 in the inlet manifold4.

Preferably the tubular sleeve is a good transmitter of the germicidalwavelengths (220 nm-280 nm).

Preferably the tubular sleeve is made of quartz.

Preferably the tubular sleeve is closed at one end 28.

Preferably the quartz sleeve is coated with a material whichsubstantially transmits the germicidal wavelengths (220 nm-280 nm).

Preferably the coating material is substantially resilient in nature andis able to contain all quartz debris in the event of the quartz tuberupturing.

Preferably the material is Teflon FEP.

Means are provided to form a small concentric gap 12 between the tubularsleeve 11 and the inside wall of the mixing sleeve 20. By selecting thedimensions of the outer diameter of the tubular sleeve 11 to be slightlysmaller than the inner diameter of the mixing sleeve 20, the gap 12produced is the dimensional difference between the two.

Means are provided to make a water tight seal between the tubular sleeve11 and the inlet manifold 4 in the form of a seal 13 positioned on thecircumference of the open end of the tubular sleeve 11 adjacent to ahole 9 in the inlet manifold. The closed end of the tubular sleeve 11 issupported by collar 21 and it is free to move inside the collar.

Any differential expansion between the reaction chamber 1 and thetubular sleeve 11 is automatically accommodated by this arrangement.

Under fluid pressure the tubular sleeve 11 with one end closedexperiences a net force which acts such as to move the tubular sleeve 11in the direction of the open end of the tube. To prevent tubular sleeve11 movement under pressure the retaining plate 22 holds the tubularsleeve 11 in position preventing any movement.

The seal 13 is compressed by a clamping plate 15 forming a watertightseal between the inlet manifold 4 and the tubular sleeve 11. Thereaction chamber 1, tubular sleeve 11 and the inlet and outlet manifolds4 & 5 form a watertight assembly such that fluid can flow in through theinlet manifold 4, through the gap 12 and out through the outlet manifold5.

Preferably the seal 13 is made of UV resistant material.

Preferably the material is silicone rubber, PTFE or FEP or another UVresistant material.

Means are provided to radiate UV germicidal wavelengths (220 nm-280 nm)into the gap 12 in the form of a lamp 17 positioned inside the tubularsleeve which when energised radiate germicidal wavelengths into the gapthrough the wall of the tubular sleeve.

Means are provided for mixing the liquid in the gap 12 in the form of amixing sleeve 20 which is rigidly fixed in a watertight manner into thereaction chamber 1.

Preferably the mixing sleeve is pressed or glued onto the reactionchamber 1 forming a water tight seal.

Preferably in order to provide an additional mixing function to thefluid film, the inside surface of the mixing sleeve 20 adjacent to thetubular sleeve 11 is formed into a pattern which when the liquid flowsthrough the gap 12 creates turbulence and hence mixing in the fluidfilm.

Preferably the lamp is positioned longitudinally centrally andconcentrically inside the tubular sleeve to provide consistent and evenradiation into the gap.

Means are provided to mix the fluid as it passes through the disinfectorin the form of mixing devices 18 positioned along the body of thereaction chamber whereby the flow in the gap 12 is diverted into andthrough the mixing device. The mixing device 18 forces the fluid flow totraverse a path which causes the fluid to change direction and hencevelocity to create a thorough mixing of the fluid as it passes throughthe device.

Preferably the mixing device 18 has no moving parts.

Preferably the mixing device 18 is made of material which issubstantially resistant to germicidal radiation.

Preferably the mixing device 18 is made of a food grade standardmaterial.

Preferably the body of the mixing device 18 is made of 316 standardstainless steel.

Preferably the internal parts of the mixing device 18 are made of PTFE,Teflon FEP or another suitable material.

Means are provided to add additional mixing in the form of a propeller23 positioned through the wall of each of the inlet and outletmanifolds. The motor and gearbox 24 is fixed to the wall of each of theinlet and outlet manifolds and is supported by a bearing and seal 27.When actuated by the motor and gearbox 24 the propeller 23 rotates inthe fluid flow and creates a high level of mixing.

The fluid to be disinfected enters into the apparatus via the inlet pipe26 through the wall of the feed manifold 25

The general fluid flow is shown by the arrows A, B, C & D.

Referring to FIG. 4 of the drawings shows a mixing device for theapparatus comprises circular flanges 2 & 3 attached to the body of thereaction chamber 1. Both flange 2 and flange 3 have smooth faces

Positioned through the centre of the reaction chamber 1 is the tubularsleeve 11 as described previously, which with the reaction chamber 1provides the gap 12.

Interposed between the two flanges is a plurality of discs 6 each dischas a series of slots 7 cut into the disc 6 radially from the centreoutwards and positioned equi-distance around the circumference of thedisc 6. Each disc 6 is positioned so that the slots in alternative discsare equi-spaced between the slots in the proceeding disc 6 such when thediscs 6 are assembled together they form a labyrinth i.e. there is nostraight fluid path through the assembled discs. Preferably the discpatterns are made and assembled such that the resulting labyrinth causesa fluid flowing through it to be forced to perform 180° bends. Thecentre hole 10 in the disc 6 is a tight fit on the tubular sleeve 11which when the mixing device is assembled the walls 9 of the disc 6substantially acts as a deflector for the fluid diverting it out of thegap 12 and forcing it through the slots 7 and through the labyrinth.

Preferably the fluid will have had many complete reversals of flowthrough the mixing device creating a thorough mixing of the fluid.

Preferably the discs 6 are made of a UV resistant material.

Preferably the disc is made from PTFE or Teflon FEP

The mixing device has an additional feature in that after CIP (clean inplace—the drinks industry standard cleaning process) the unit selfsterilizes if at the end of the cleaning cycle if it is filled withwater and the lamp is switched on for a period of time, there is enoughradiation to reflect through the mixing device to disinfect it.

FIG. 4 only shows three discs 6 but a plurality of discs can bepositioned in series to increase the level of mixing of the fluid.

Those skilled in the art will appreciate that the mixing effect can beaccomplished with many different labyrinth-like patterns in the mixingdevice of which the general theory of the invention covers.

It should be noted that known static mixers do not create flow reversali.e. 180° bend: they blend a liquid by manipulating it always in aforward direction and hence need a sizable longitudinal component toeffect the mixing. The mixing devices in this invention effect themixing over a short distance by flow reversal and hence a plurality ofmixing devices can be employed over a short distance.

Referring to FIGS. 6 an 7 of the drawings, a fluid treatment systemcomprises twenty plurality of fluid treatment apparatus 99 of the kinddisclosed in FIG. 1 mounted side-by-side in a housing 105. Eachapparatus 100 comprises an elongate tubular duct 100 having a fluidinlet and outlet 101,102 at opposite ends thereof an elongate source ofUV radiation 104 extending longitudinally of the elongate tubular duct100. A plurality of mixing devices 103 of the kind disclosed in FIG. 4or 5 are disposed between adjacent longitudinal portions of each duct100 for diverting all of the fluid flowing along the duct through fluidmixing formations in the device 103 and for returning the mixed fluid tothe duct.

The outlet and inlets 101, 102 of adjacent apparatus 99 are connected toeach other via respective manifolds 106. In use, fluid flows downwardlyfrom an inlet duct 107 into the first apparatus 100 and then through amanifold 106 and upwardly through a second apparatus 100 and so on untilthe fluid flows out of the last apparatus 99 into an outlet duct 108.

Referring to FIG. 8 of the drawings, a fluid treatment comprises anelongate tubular duct 110 having an elongate source of UV radiation 111extending longitudinally of the elongate tubular duct 110. A pluralityof mixing devices 112 are sealingly fitted between disposed betweenadjacent longitudinal portions the duct 110 for diverting all of thefluid flowing along the duct 110 through fluid mixing formations 113 inthe device 112 and for returning the mixed fluid to the duct 110.

Each device 112 depends from the duct 110 and is mounted entirely belowthe level of the flow passage 114 therein to ensure that no high spotsexist in which air may become trapped. The device 112 comprises a flowpath having an inlet duct 115 which extends perpendicular to thelongitudinal flow axis of the passage 114. The path then comprises aseries of formations 113 which turn the fluid flow through 180° anddirect it at a baffle wall where it is deflected into another formation113 ensuring that the fluid is thoroughly mixed. Fluid then leaves thedevice 112 through a flow an outlet duct 117 which extends perpendicularto the longitudinal flow axis of the next section of the passage 114.

The formations 113 are formed in the opposing faces of plates 118,119which are clamped together against a central plate 120 formed withapertures 121 that communicate between the formations 113. The plate 120and or plates 119,120 may be formed of a material which transmits UVradiations so that the flow path is sterilised by the radiation from theUV source 111.

Referring to FIG. 9 of the drawings, there is shown an embodiment whichis similar to the embodiment of FIG. 8 but which is simpler inconstruction.

The presention invention thus provides a fluid treatment apparatusparticularly for sterilising drinks which comprises an elongate tubularduct and an elongate UV light source extending longitudinally of theduct. A mixing device disposed between adjacent longitudinal portions ofthe duct diverts all of the fluid flowing along a first portion of theduct through fluid mixing means in the device and returns the mixedfluid to a second portion of the duct. The fluid flows longitudinally ofthe duct in a thin annular low passage which extends around the UV lightsource. Micro-organisms in the resultant thin flow of fluid are killedas they come within close proximity of the light source. The mixingdevice causes all of the flow to be thoroughly mixed and returned to theflow passage. The preferred provision of a plurality of mixing devicesalong the length of the duct increases the likelihood that allmicroorganisms receive a sufficient lethal dose of UV radiation.

1-20. (canceled)
 21. A method for treating a fluid, comprising: flowinga fluid along an elongate tubular duct having a fluid inlet and a fluidoutlet at opposite ends thereof; mixing said fluid by diverting all ofthe fluid flowing along a first portion of the duct through a mixingdevice; returning the mixed fluid to a second portion of the duct; andirradiating the fluid flowing in the first and second portions of theduct with UV radiation.
 22. The method of claim 21 wherein diverting allof the fluid comprises diverting all of the fluid through a tortuousflow path.
 23. The method of claim 21 wherein diverting all of the fluidcomprises diverting all of the fluid through one or more turns of atleast 90°.
 24. The method of claim 23 wherein diverting all of the fluidcomprises diverting all of the fluid through 180° between adjacentlongitudinal portions of the duct.
 25. The method of claim 24 whereindiverting all of the fluid comprises diverting all of the fluid throughsuccessive turns.
 26. The method of claim 21 wherein mixing the fluidcomprises directing the fluid against one or more baffles.
 27. Themethod of claim 21 wherein irradiating the fluid with UV radiationcomprises irradiating a flow path of fluid flowing along the duct. 28.The method of claim 27 wherein irradiating the fluid comprisesirradiating the fluid with a source located no more than 10 mm away fromthe flow path.
 29. The method of claim 21 wherein irradiating the fluidcomprises irradiating the fluid flowing in the first portion of the ductbefore it flows through the mixing device, and irradiating the fluid inthe second portion of the duct after it has flowed through the mixingdevice.
 30. The method of claim 21 wherein irradiating the fluidcomprises irradiating the fluid with a UV source extending along acentral axis of the duct surrounded by the fluid flow.
 31. The method ofclaim 21 wherein irradiating the fluid comprises irradiating the fluidwith an elongate UV source comprising an elongate lamp disposed inside atube.
 32. The method of claim 21 comprising coating or covering the UVsource with a material arranged to maintain the integrity of the tubeshould it break.
 33. The method of claim 21 wherein mixing said fluidcomprises mixing said fluid through a plurality of mixing devicesprovided along the length of the duct.
 34. The method of claim 21comprising flowing said fluid through respective manifolds incommunication with the inlet and/or outlet of the duct.
 35. The methodof claim 34 wherein irradiating the fluid comprises irradiating thefluid flowing in one or both manifolds.
 36. The method of claim 35further comprising mixing the fluid in each manifold.
 37. A method fordisinfecting a fluid comprising: flowing a fluid along a plurality ofelongate tubular ducts each having a fluid inlet and a fluid outlet atopposite ends thereof, wherein fluid is flowed along the tubular ductsarranged in at least one of in parallel and in series; mixing all ofsaid fluid by diverting all of the fluid flowing through each ductthrough at least one mixing device; and irradiating the fluid with UVradiation.
 38. The method of claim 37 wherein diverting all of the fluidthrough the at least one mixing device comprises diverting all of thefluid flowing through a plurality of mixing devices, wherein each of theplurality of mixing devices is coupled to a separate, corresponding oneof the plurality of ducts.
 39. The method of claim 38 wherein mixing allof said fluid comprises diverting all of said fluid flowing through afirst portion of the ducts through the mixing devices and returning thefluid to a second portion of the ducts.
 40. A method for treating afluid, comprising: transporting a fluid flow via a fluid transportmeans; irradiating fluid flowing in said transport means with a UVirradiation means; mixing fluid flowing in said transport means with amixing means, wherein the mixing means diverts all of the fluid flowingalong a first portion of a duct to a second portion of a duct.
 41. Themethod of claim 40 wherein mixing fluid flowing in said transport meanswith a mixing means comprises diverting all of the fluid through atortuous flow path.
 42. The method of claim 21 wherein mixing said fluidcomprises diverting all of the fluid flowing through a labyrinth-likepattern.
 43. The method of claim 40 wherein mixing said fluid comprisesdiverting all of the fluid flowing through a labyrinth-like pattern.